Gear/Drive splitter???

[Jon Fuller]

I know Michael Hewland. I used to work with his brother.

Did a tour of the plant in Maidenhead back in the 80's.

Last saw Michael at his brothers funeral a couple of years ago. His son William runs the show now, as Michael has retired. clever fella.

[PerformanceDodge]

Originally Posted by Jon Fuller

I know Michael Hewland. I used to work with his brother.

Did a tour of the plant in Maidenhead back in the 80's.

Last saw Michael at his brothers funeral a couple of years ago. His son William runs the show now, as Michael has retired. clever fella.

They did some work for a friend of mine who is building a jet pack (www.jet-pack.co.uk) apparently they are a very clever company. If James had a large race budget I'm sure they would be the ideal company.

If you take into account 100kg for the second drive, around 50kg for a belt drive system or probably 100kg for a geared system, 5 to 10% power loss through the drive system, the 3/8 extra fuel load to produce 800hp as opposed to 500hp, the drag of two drives and props as opposed to one, you would probably end up back were you started or slower.

A lesser tuned engine would be more reliable, two drives to go wrong instead of one, belts or gears to fail, a lot of time and effort and a considerably lighter wallet would not make it worth wile. Now if it was a 35ft lightweight boat with single 1000hp engine and surface drives it may be worth the effort. If you had a large race budget.

At the end of the day it is really only a concept idea and I am sure as you say he would be better sticking to 500hp and single drive than twin drives and 800hp.

[larby]

Wow, this has really taken off!!
I must admit, this one was more of a 'hey, I've had this crazy idea' job than something I actually plan to do. As Freddy pointed out and I had realised at the start, with my relatively low power output, I'd probably end up going slower.
That said, had we found a cheap way of doing it, it could've been worth it as I've already got two bravos and I do like to be different!

I've had a long chat with a couple of people who, unlike me, know what they're talking about and it'd seem my best chance by far is to get a DPX if I stick with a blower.

Another interesting avenue suggested by Peter Unwin (thanks!) was that I gain speed by changing engine for a small block aluminium lump and therefore saving a shedload of weight, aim for about 400hp and I should see a better speed.

James

[Cookee]

Originally Posted by freddy21

Hi Cookey, “Belts in cars drive the camshaft not the gearbox though - there is also a lot more shock through a boat drive when the boat re-enters the water after a jump ............. just my thoughts ............”

Tooth belt drive will handle quite high shock loads, not sure of the foot pounds torque at the rear wheel of my Buell bike, but you can drop the clutch in first gear and being a 100hp V twin with a heavy flywheel they don’t break belts, and that is only a 35mm wide belt. There is also a V twin drag bike race series, think they put out about 600hp. The drive between the engine and transmission is belt drive so again with high shock loads off the line don’t think this would be a problem in a boat.

Two questions:

How much does your bike weigh?

How often to you land a jump on your bike at full throttle?

[PerformanceDodge]

Hi Cookee

Probably around 300kg with me on it and I try to keep the wheels on the ground

All joking apart belt drives belts are quite good at shock loads when sized correctly and can handle quite high loads.

Below is a picture of the drive belt on a top fuel drag bike, they all use primary belt drive between the engine and clutch and most put out around 1000hp

The link below is to a You tube video of a top fuel drag bike leaving the line, dumping the clutch at full power is a massive shock load. I have seen many blower belts fail usually due to the engine spitting back and locking the blower, but never a primary drive belt fail on a drag bike. I suspect if you had a clutch on a boat and dropped it at max revs the gearbox would go before the belt drive.

http://www.youtube.com/watch?v=VKe74wWwteM

[Paul E]

The clutch on a top-fuel or supertwin drag bike is pre-set to come in gradually after the hit of the throttle off the line. They have no gearbox as such, the clutch and fuel/timing systems control the power delivery gradually throughout the run.

If the clutch were to completely lock on the hit they'd sit there smoking the tyre and not going anywhere It would be interesting to know how much stick those belts could actually take though, I'd imagine there's massive loads throughout the 1/4 mile and on full clutch lockup over the line with those huge sticky slicks. Awesome bits of kit ridden by true lunatics!

[Cookee]

Originally Posted by Paul E

The clutch on a top-fuel or supertwin drag bike is pre-set to come in gradually after the hit of the throttle off the line. They have no gearbox as such, the clutch and fuel/timing systems control the power delivery gradually throughout the run.

My point exactly, not dumping the clutch at 1000hp! and what is the life of a belt? I know the top fuel drag race cars have some components life measured in seconds!

It's probably not worth doing this discussion to death, but without doing the full research I can't see a belt used in the way you describe ever being any good in a high performance or race boat situation, having seen the sort of kit that gets broken in offshore situations I wouldn't even try one in a boat if it was my money and I would try and talk a customer out of trying one as well!

[PerformanceDodge]

Originally Posted by Cookee

My point exactly, not dumping the clutch at 1000hp! and what is the life of a belt? I know the top fuel drag race cars have some components life measured in seconds!

It's probably not worth doing this discussion to death, but without doing the full research I can't see a belt used in the way you describe ever being any good in a high performance or race boat situation, having seen the sort of kit that gets broken in offshore situations I wouldn't even try one in a boat if it was my money and I would try and talk a customer out of trying one as well!

Hi Cookee

A year ago I new nothing about building power boats and a little bit about engineering, but thanks to this for forum and the great wealth of knowledge and experience gathered over many years of racing by you guys, I have learned quite a bit a year down the line I now know a little bit about boats too, but I would have a long way to go before I would have the knowledge of you guys.

Before I bought my Cougar you advised me to check over it carefully as most have been repaired, hind sight is a wonderful thing and I wish I had of paid you for an hour of your time to look over it and take some advise from you before I bought it. What I didn't know at the time is that they are made with a Vinylester resin and some of the repairs and mods had been done with Polyester without even keying the surface, result was when I got a screw driver behind the repairs the came away like bacon on a non stick pan. So the cheep hull I bought which some of the repairs needed redoing with epoxy has not turned out to be such a cheep hull, hey ho still chuffed to bits with it and enjoying the project.

My point being, I'm a newby to this and with your experience I am sure you are right about the belt drive idea, but its been an interesting thread and without new ideas, experimentation and expanding the boundaries we would never move forward.

ps think your build tread is great and can wait to see it race.

Regards David

[Cookee]

Vinylester is a great product until you need to repair it! As race boats tend to need repairing for one reason or another we will not build in that material unless a customer demands it and Kitten agrees to use it!

Looking forward to seeing how the diesel goes in one of those hulls - time will tell!